1. Field of the Invention
The present invention relates to the evaporative air cooler art.
2. Description of the Prior Art
Air handlers having evaporative coolers, of the type to which the present invention particularly relates, include a housing defining a conditioning chamber in which the air is cooled and/or humidified as a fan moves or recirculates space air through the chamber. The housing may also define other chambers or zones in which some other conditioning (e.g., heating, pre-filtering, dehumidifying) may occur. The evaporative cooler includes an air permeable, fluid retaining pad which is disposed transversely to the direction of air flow through the conditioning chamber, and a water delivery system is provided for keeping the pad moist. In the field of evaporative air cooling, it is well known that sensible heat from warm, unsaturated air passing through a wetted evaporative pad is, in part, transferred to the water in the pad. Ideally, the sensible heat of the air is converted into latent heat through evaporation of the water throughout the pad and the water vapor mixed into the air stream. In this way, the air moved through the air handler is cooled. In order for evaporative cooling to continue, water removed from the pad by evaporation or otherwise must be replaced.
Present systems for delivering water to the pad fail to maintain an adequate and relatively uniform moisture level in the pad. The development of major dry areas on the pad reduces efficiency because warm, unconditioned air will by-pass normal evaporative heat exchange through the moisture barrier areas on the pad and become mixed with the conditioned air on the downstream side of the pad thereby decreasing the cooling potential and efficiency. In some instances, pads have become completely dry before resoaking, causing scaling of the pad and the development of deposits on the pad. Scaling and deposit formation on the pad reduce its air permeability and the useful life of the pad. Attempts to avoid scaling and deposits by constantly bleeding water onto the pad and flushing the pad have been of limited success and cause water to be wasted. Moreover, existing evaporative coolers are not responsive to changes in the state of the incoming air. Changes in temperature and water content of incoming air will cause water to be evaporated more or less rapidly from the pad. Therefore, depending upon the state of the incoming air, the amount or frequency of soaking of the pad may be far more than needed, causing water to be wasted, or may not be enough to prevent dry spots from developing on the pad.
Occasionally, unpleasant odors may be introduced into the conditioned air when an air handler has begun moving air through the pad before soaking of the pad. The introduction of odors typically occurs when the air handler is first activated. The problem of odor is exacerbated by the use of recirculated water to the pad, as is common in existing air handlers. Recirculated water is more likely to have debris in it which can clog the nozzles or other orifices through which water is delivered to the pad, causing uneven soaking of the pad. Moreover, recirculated water tends to pick up heat as it is being circulated, causing less heat to be transferred from the air in the pad. However, recirculating water delivery systems are presently used in order to conserve water.
The water retaining pad of a prior art evaporative cooler is positioned with its upstream side lying in a plane transverse or perpendicular to the direction of air flow through the air cooling chamber. Air moves through the pad relatively quickly, thereby limiting the amount of heat transfer which occurs. Moreover, the rapid air flow through the pad tends to push some of the unevaporated water out the downstream side of the pad, causing the pad to lose water without the cooling benefits associated with water loss by evaporation. The problem of unevaporated water being carried through the pad is made worse by the presence of too much water in the pad. Frames supporting the pads usually have louvers which reduce the pad surface area facing the air flow, and cause increased air velocities through the pad.